1. Field of the Invention
The present invention relates to a resin composition with good heat stability and weather resistance. More particularly, the present invention relates to a resin composition which has good heat stability and weather resistance and comprises a resin, a hindered piperidinyloxy compound and a hypophosphite compound.
2. Description of the Related Art
The amount of resins used outdoors is increasing year by year. Such use of these resins is required to have weather resistance according to the particular application used. To this end, various weathering stabilizers have been developed. Recently, hindered amine base weathering stabilizers, which are so-called hindered amine light stabilizers (HALS), are often used, since they can prevent a decrease of the mechanical properties or a change of color tones of the resin compositions when subjected to outdoor weathering, much better than the conventional weathering stabilizers (cf. Japanese Patent Kokai Publication No. 86645/1984).
Since weathering stabilizers cannot impart processing stability or heat stability to the resins, a heat stabilizer (e.g., hindered phenol base heat stabilizer, a sulfur base heat stabilizer and a phosphite ester base heat stabilizer) is generally added to the resin composition.
However, the heat stabilizing effect of the hindered phenol base heat stabilizer, which is added to the resin to impart processing stability and heat stability to the resin, may be deteriorated by the hindered amine base weathering stabilizer, or the resin composition may be discolored.
A hindered piperidinyloxy compound which can be derived from a hindered amine base weathering stabilizer, has substantially the same weathering stabilizing effect as the corresponding hindered amine type weathering stabilizer, and also has a heat stabilizing effect. However, its heat stabilizing effect on the resin composition is insufficient in comparison to the hindered phenol base heat stabilizer.